Theodore J. Lowi, a venerated political scientist who challenged conventional scholarship on presidential power and identified the emergence of what he called “interest-group liberalism,” died on Feb. 17 in Ithaca, N.Y. He was 85.

His death was confirmed by his daughter, Anna Lowi.

Professor Lowi taught at Cornell University from 1959 to 1965, returned in 1972 and remained the John L. Senior professor of American institutions until he was granted emeritus status in 2015.

Coupling academic expertise with charisma, he popularized his theories with an evangelical zeal and a Southern drawl in lectures, television appearances and groundbreaking books, which he was said to have dictated verbatim into a tape recorder.

They included “The End of Liberalism: The Second Republic of the United States” (1969), “The Politics of Disorder” (1971), “American Government: Incomplete Conquest” (1976) and “Hyperpolitics: An Interactive Dictionary of Political Science” (2010), written with Mauro Calise. He also edited “The Pursuit of Justice” (1964), Robert F. Kennedy’s book about his tenure as attorney general.

Writing in The Nation in 1969, he was among the first political scientists to describe New York City as “ungovernable” — urging Mayor John V. Lindsay to declare that the city could not survive without a regional government through which suburban wealth would subsidize solutions to urban crises.

Professor Lowi was named the nation’s most influential political scientist in a poll of the American Political Science Association’s members in 1978. He was the president of that group in 1991 and of the International Political Science Association from 1997 to 2000.

“Lowi’s scientific personality was a unique mix of extraordinary empirical knowledge and bold theoretical vision,” Ilter Turan, the president of the international association, said in a statement.

In his seminal study of liberalism — philosophical rather than political — Professor Lowi wrote that “modern liberalism has left us with a government that is unlimited in scope but formless in action,” a government that “can neither plan nor achieve justice because liberalism replaces planning with bargaining and creates a regime of policy without law.”

He argued that special-interest politics began during the New Deal and fragmented power further with the decline of the two-party system “to replace elected representation with interest groups as proxies for citizen participation.” Those groups, he wrote, could paralyze government and thwart the popular will.

Critiquing Professor Lowi’s “The Personal President” in The New York Times Book Review in 1985, Hendrik Hertzberg praised “The End of Liberalism” as an “influential and highly original work” and summed up “The Personal President” this way:

“Mr. Lowi shrewdly describes the presidency as an increasingly ‘plebiscitary’ office. Its occupant uses television and polls to commune directly with the masses, bypassing such mediating institutions as Congress and the political parties. Having given our presidents big power, we expect big things of them — especially in terms of ‘service delivery,’ which, Mr. Lowi writes, has displaced representation as the test of democracy and legitimacy.

“Despite the aggrandizement of the executive branch at Congress’s expense, though, there are still ‘built-in barriers to presidents’ delivering on their promises,’” Mr. Hertzberg continued. “The result is a dangerous cycle — substantive failure, followed by frantic White House efforts to create false images of success, followed by adventurism abroad, followed by further public disillusion — all of which forces the next president to turn the rhetorical heat up even higher.”

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Mr. Lowi speaking at the Arch Dotson Memorial Symposium at Cornell University in 2006.CreditCornell University

Professor Lowi acerbically coined what he called the “Law of Succession,” which holds that each new president enhances the reputation of his predecessors. He also posed a corollary: “This is the only certain contribution each president will make.”

Theodore Jay Lowi was born on July 9, 1931, in Gadsden, Ala., to Alvin Rosenbaum Lowi, who founded a chemical company, and the former Janice Haas, a piano teacher and silent movie accompanist.

Israel Sergio Waismel-Manor, a lecturer at the University of Haifa in Israel and a former student of Professor Lowi’s, wrote of him in February, “He was not a religious person, but coming from the Deep South, and having played music with his mother and his siblings at the local Jewish temple, he was really an Evangelical, a preacher who followed his own apostles: Jefferson, Madison, Hamilton and V. O. Key.”

An illness forced Mr. Lowi to drop out of Tulane University, but he recovered — determined, he once said, someday to “be in the history books.” Instead, he would write them.

He attended Michigan State University on a music scholarship (he played the oboe) and graduated in 1954. He earned a master’s and a doctorate in political science from Yale.

His first marriage ended in divorce. His second wife, the former Angele Marie Daniel, died in 2015. In addition to their daughter, he is survived by their son, Jason; his brothers, Alvin Jr. and Bertram; and his sisters, Jan Horn and Bettie Baer.

Professor Lowi maintained that “political science is a harder science than the so-called hard sciences because we confront an unnatural universe that requires judgment and evaluation.”

That was one reason he sought to expose Cornell students to practical politics with an undergraduate program for research and teaching in the nation’s capital.

His own political experience was uninspiring. In 1958, he managed the campaign of George Hawkins of Gadsden in the Democratic primary for governor of Alabama. Mr. Hawkins finished sixth in a field of 14.

He also campaigned for Senator Eugene McCarthy in the 1968 Democratic presidential primaries and was an advocate for third-party presidential candidates, including Representative John B. Anderson, who ran and lost in 1980.

Despite those losses, Professor Lowi’s fervor was undiminished.

“Among the sins of omission of modern political science, the greatest of all has been the omission of passion,” he said in a speech to the American Political Science Association when he completed his term as president.

He did not mean the passion of ideology, he explained, but “the pleasure of finding a pattern, the inspiration of well-rounded argument, the satisfaction of having made a good guess about what makes democracy work, and a good stab at improving the prospect of rationality in human behavior.”

He continued: “This is not an opportunity to play philospher-king. It is an opportunity to meet our own intellectual needs while serving the public interest. And we need not worry how to speak truth to power. It is enough to speak truth to ourselves.”

A version of this article appears in print on , Section B, Page 8 of the New York edition with the headline: Theodore Lowi, an Influential Academic on Presidents and Liberalism, Dies at 85. Order Reprints | Today’s Paper | Subscribe